Embryos depend on maternally-encoded mRNAs and proteins until the onset of zygotic transcription. Maternal mRNAs are regulated both at the level of translation and RNA stability. Cytoplasmic mRNA processing bodies, termed P-bodies, have been implicated in the degradation and translational repression of mRNAs in yeast and mammalian cell culture, but have yet to be studied in the context of a multicellular organism. Preliminary data suggests three types of distinct P-body related RNPs exist in early C. elegans embryos. The goal of this project is to identify the mechanisms by which P-bodies function to regulate distinct maternal mRNA fates in different embryonic cell types. This will be carried out by first analyzing the distribution and dynamics of P-body components in the early embryo using co-localization studies in fixed and live samples, and through RNAi-mediated knockdown of individual P-body components. Second, the function of P-body components in the degradation and translational repression of maternal mRNAs will be analyzed through the use of in situ hybridization, quantitative reverse transcription PCR, and translational reporter assays. Lastly, regulators of P-body related RNP localization and assembly will be identified using a focused, RNAi-based screen. In this screen, the localization of two P-body components that I have found to localize to distinct classes of P-body related foci will be examined after RNAi-mediated knockdown of ~3,000 genes expressed preferentially in the female germline. By systematically analyzing the distribution and function of conserved P-body components in C. elegans embryos, this project will further our understanding of how post-transcriptional gene regulation contributes to cell diversity in development. P-bodies have been implicated in the maintenance of proper gene expression during times of stress in both yeast and mammalian cells. Also, P-body components are often the target of autoantibodies in humans, and some P-body components are often misexpressed in various cancers. Understanding the function of P-bodies in a multicellular organism in a developmental context will lead to a better understanding of the role of this machinery in stress response, disease, cancer progression and the developmental process. [unreadable] [unreadable] [unreadable]